The present invention relates to dental chairs and more particularly to an expandable legrest for a dental chair.
A conventional dental chair often includes adjustable seatrest, backrest and legrest sections. With such an arrangement, the chair sections can be moved so as to accommodate either a seated or a reclining patient. In this respect, the back and legrest sections would be substantially vertically oriented for the seated patient and horizontally oriented to accommodate a reclining patient.
A patient who is seated upright in a dental chair will find that his legs overhang the legrest as the legrest and backrest are moved to the horizontal position. The reason for this is that the pivot of the legrest does not coincide with the knee joint which is the pivoting point for the patient's leg. Accordingly, as the legrest pivots from the vertical to the horizontal position, it travels through a shorter arc length than the patient's leg resulting in the patient's foot overhanging the legrest when the legrest is horizontal. This is shown schematically for example in FIG. 1 of the drawings.
One way in which the prior art overcame this problem was to eliminate the legrest and simply provide a lounge type of chair, wherein the legrest is an extension of the seatrest. Another way is to pivot a relatively long legrest section to the seat of the chair. However, in this case, the legrest cannot be moved to a near vertical position because it will hit the floor surface when the chair is moved to a low position.
In the present invention, the legrest has telescoping sections which elongate as the legrest is moved from a vertical position, accommodating the seated patient, to a horizontal position, accommodating a reclining patient. Conversely, as the chair moves from a reclining to an upright position, the telescoping legrest shortens. The elongation and the shortening of the legrest occurs automatically and in direct proportion to the inclination of the legrest.